Multicollector ICP Mass Spectrometry

The ICP-MS laboratory is equipped with a Finnigan Neptune multi-collector ICPMS in addition to the ELEMENT-XR ICPMS. The Neptune is a double focusing, high-resolution multi-collector mass spectrometer for high precision isotope ratio measurements. It has 9 Faraday collectors and 8 ion counting electron multipliers allowing simultaneous measurement of several isotopes in static mode. The ion counter collector array is optimized for static measurements for U-Th-Pb geochronology and common lead isotopic tracer studies.

The Neptune can be set to three different resolution modes (low, medium and high resolution). At high resolution, molecular interferences can be separated from elemental peaks of interest.

Sample introduction to the MC-ICPMS is mainly as metal-specific solutions purified by anion exchange chromatography in the clean lab complex. An Apex Q sample inlet system provides sensitivity enhancements of factors of 3 to 10 over conventional spray chambers with extremely fast rinse-out times. Development of the system is initially focused on measurements of U, Th and Sm for the new joint Dalhousie-Memorial U-Th-Sm/He thermochronology facility, the first of its kind in Canada.

The MC-ICPMS may also be coupled to the 193 nm excimer laser for in situ isotopic measurements. Initial laser ablation MC-ICPMS studies are concerned with lead isotopes in sulfides and plagioclase, and hafnium isotopes in zircon.